1. Field of the Invention
The present invention relates to a device for reducing dead space in a ventilator system, as well as to a ventilator system employing such a device.
2. Description of the Prior Art
In the mechanical ventilation of a patient with a ventilator system (in intensive care, anesthesia etc.), an abnormal amount of dead space develops for the patient. The term xe2x80x9cdead spacexe2x80x9d refers to the volume in which there is no gas exchange. As a result, expired gas in the dead space is returned to the patient at the next inspiration. The ventilator system""s dead space mainly consists of the connection between a Y-piece and the patient (e.g. a tracheal tube and humidifier/heat exchanger and a measurement tube for measuring gas contents, flow, pressure etc.) Dead space can be relatively large, depending on the design of the ventilator system.
Since, as a rule, the last gas expired in every breath contains the highest concentration of carbon dioxide, the larger dead space causes greater re-breathing of carbon dioxide.
U.S. Pat. No. 5,400,778 describes a ventilator system containing a device for reducing the re-breathing of carbon dioxide. In one embodiment, gas is suctioned out of a tracheal tube while gas is delivered at the same time by the ventilator system through an inspiratory line. Additional gas can be supplied through additional connected lines, making it necessary to compensate the regulation of flows for the different volumes supplied to and evacuated from dead space.
Although the known device/ventilator system functions well, there is still a desire to achieve a device producing the same or equivalent effects with a simpler construction, especially with regard to control over-evacuated and delivered gas. Achieving a device that can be easily moved between different ventilator system, regardless of the design and application, would also be desirable. Another desire is to achieve a device that ensures simple maintenance of device functionality in the event of a power failure etc.
An object of the present invention is to provide a device that fulfills one or more of the aforementioned desires.
The above object is achieved in accordance with the principles of the present invention in a device for reducing dead space in a ventilation system having a first tube connectable to dead space in the ventilator system for producing a flow path for transport of gas from the dead space, a suction unit connected to the first tube for generating an adjustable negative pressure in the first tube, a second tube connectable to the dead space for producing a flow path for transport of gas to said dead space, a pump connected to the second tube for generating an adjustable positive pressure in the second tube, the suction unit and the pump being formed respectively by a first chamber and a second chamber in an enclosure with the first and second chambers being separated by a gas-tight, movable partition, and a control unit for regulating the suction unit and the pump by moving the partition.
A suction unit connected to a pump is achieved in an embodiment wherein enclosure is provided with two chambers separated by a moving partition. The interconnected suction unit and pump unit make it possible to achieve simultaneous evacuation and delivery of a selected volume of gas in a simple and effective fashion. The chambers are connected to dead space via the tubes, and the entire device is compact and easy to transport and move between different kinds of ventilator systems.
The first chamber can be devised with an evacuation unit in order to empty the suction means when the movable partition moves back and forth. In the corresponding manner, the second chamber can be devised with a gas connection for delivering fresh gas. Here, the gas connector can be connectable to the ventilator system. This provides the advantage that no separate gas supply is necessary.
When equipped with a signal input for receiving signals, the device is able to receive signals from the ventilator system. Especially signals indicating where the ventilator is in the breathing cycle. The device is for activation primarily during the end phase of expiration (or during a pause following expiration) in order to reduce dead space in the ventilator system.
Information about the breathing cycle can alternatively be obtained from a flow meter arranged in the ventilator system""s expiratory components.
Increased accuracy in maintaining a volume of evacuated gas of the same magnitude as the volume of gas delivered is achieved by connecting a first manometer to the first tube or first chamber and a second manometer to the second tube or second chamber. For additional accuracy, pressure in dead space can be determined, either by means of a signal from the ventilator system or by a separate, third manometer connectable to the ventilator system""s dead space. When the prevailing pressure (and pressure gradient) is(are) known, the device can be controlled to ensure that the volumes evacuated and delivered are virtually identical.
The device can be completely integrated into a ventilator system.